While searching for a serial killer in Berlin's tunnel system, investigator Maik Brunner is hit by a subway train. He wakes up in hospital - in the GDR, in 1984! Lieutenant Kempe is already waiting for him - she is working with him on a series of murders very similar to the one in 2009. Here, too, the perpetrator has poisoned his victims. And here, too, he knows his way around the underground. If Brunner catches the perpetrator in 1984, he could save his girlfriend. In 2009, she is in the hands ...